As illustrated in FIG. 1, a hybrid driving system which is applied to a commercial hybrid electric vehicle (HEV) is configured to include an engine 1, a clutch actuator 2, a driving motor 3, and automatic manual transmission (AMT) 4. The AMT 4 has a structure in which an automatic shift actuator 5 is mounted in the existing manual transmission and a clutch automatic release unit is mounted therein.
The AMT-HEV (hybrid electric vehicle in which the automatic manual transmission is mounted) 6 stops an engine at the time of stopping and re-starts the engine 1 with the driving motor 3 which is directly connected to an input shaft of the AMT 4 at the time of re-starting. To re-start the engine 1, the AMT 4 maintains a neutral state. After the engine 1 re-starts, the AMT 4 is in a starting stage state and the hybrid electric vehicle starts with power generated from the driving motor 3 as a driving force.
However, as illustrated in FIG. 2, when the vehicle stops and then re-starts, teeth of a clutch gear 8 which are formed at a gear 7 implementing the starting stage of the AMT 4 and teeth of a synchronizer sleeve 9 form a straight line and thus the gear 7 is not engaged with the synchronizer 11 but the teeth of the clutch gear 8 collide with the teeth of the synchronizer sleeve 9, such that a blocking phenomenon that a gear engagement fails may occur.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.